Photography and Light
Light is everything in Photography and there are some concepts pertaining to light which Photographers need to appreciate and master as part of their craft. We don't need to treat light as a full blown science to become accomplished Photographers but the list below provides us with enough to illumination to allow us to grasp some fundamental characteristics of light which we can easily learn, control and manipulate to our advantage.
Light Sources
Natural - sunlight, moonlight, stars, fire
Artificial - neon lights, ordinary light bulbs, fluorescent tubes, halogen lamps
Artificial light requires more control than natural light and often needs colour correction
The Visible Light Spectrum
Light consists of wavelengths vibrating in the visible part of the electromagnetic radio spectrum and light graduates from Red to Blue and includes all the colours of the rainbow in between
Wavelengths at the red end are longer and warmer than blue wavelengths
Wavelengths at the blue end are shorter and cooler than red wavelengths
The Colour Temperature of Light
The Physics behind light waves are of interest to lens designers but Photographers think more in terms of the colour characteristics of light because it more practical to do so. The main characteristics of interest are the light's colour (hue) and whether it is neutral or has a warm (red) or cool (blue) bias
Colour Balance
Colour balance, often known as white, gray or neutral balance, relates to the overall mixture of the red, green and blue channels within in a digital image. Images in which any one channel is dominant over the others will appear to have a colour cast that will be most noticeable when looking at the white, gray and black areas of the image. This is why cameras and digital imaging editors have so many features for individually manipulating the Red, Green and Blue channels in a digital image. Whites, grays and blacks should appear neutral unless you are using colour balance for creative effects
Colour Correction
With outdoor light high contrast is the main problem to overcome and this is when landscape photography filters can come to the rescue. Sometimes a Landscape Photographer will use a warming or cooling filter for aesthetic reasons but controlling high contrast is a more important concern than is colour temperature. Digital Cameras have automatic white balance settings which may give good results but it is better to set the white balance manually and take a couple of test shots to make sure your colour balance looks right in camera. Getting the colour balance right in camera saves a lot of time and effort later in the post processing stage and results in better quality images since you are not degrading the image quality by making unnecessary and heavy handed colour adjustments
Light Metering
Most cameras have built in light meters which measure the amount of light reflected from the scene onto the light sensor and the camera's metering system uses this measurement to decide which exposure settings (shutter speed / aperture combinations) are available to take a correctly exposed shot. A good camera will offer several methods of light metering where you can take exposure readings from either the whole scene or a small part of the scene. Fine grained control of exposure can be achieved with a good understanding of camera metering system methods (particularly spot metering) and exposure compensation controls
The Human Vision System
Humans have an amazing vision system capable of detecting a far greater range of light than can a digital camera. In Photography speak this is called dynamic range and the dynamic range of a camera is nowhere near that of your eyes. Our eyes and brain act like the ultimate camera in that light detection, focusing and compensating for light and dark values is carried out at a super fast rate using an almost instant continuous feedback loop. This is one reason why we need to understand the limitations of digital imaging technology
Reflected Light
Everything we see is the result of reflected light and different objects reflect and absorb light in varying amounts. A black gemstone absorbs all incident light and reflects none whereas a red gemstone absorbs all wavelengths of light but reflects red
Environmental Effects on Light
As light travels it is affected by particles and moisture in the atmosphere which reflect and absorb light. On dry clear sunny days with little humidity in the air the light is direct and looks clean and sharp with strong colours and shadows. If the sky is overcast the light can appear more even and diffuse with colours taking on a pastel appearance and the shadows subdued
To be continued